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Neuroradiology Case of the Week

Case 121

Sudhir Kathuria, MD and Per-Lennart Westesson, MD, PhD, DDS

Clinical Presentation: A 32-year-old female presented with seizure four days after a spontaneous vaginal delivery. She had epidural anesthesia during the labor.

Radiological Findings: Contrast enhanced CT showed enhancement of meninges especially along the cisterns, sylvian fissure and tentorium. Also noticed are flame-shaped hypodensities in both occipital lobes suggestive of edema. Basal cisterns and fourth ventricle were effaced (Fig. 1).
     Axial FLAIR images showed symmetric abnormal signal intensity, primarily in the posterior circulation territories. There is also involvement of the frontal lobes. The affected area predominantly involve the white matter, with some involvement of the cortex (Fig. 2).
     MR examination, on post-gadolinium T1-weighted images showed uniform and continuous enhancement of the pachymeninges, a pattern typically seen in patient’s with intracranial hypotension. As demonstrated in CT exam, there is diffuse swelling of the brain with effacement of the cortical sulci and extra-axial spaces. The ventricles appear slit-like but otherwise maintain their configuration. Also visible is a small subdural collection on the left side (Fig. 3).
     The follow-up MR axial FLAIR images three days later show significant resolution of the lesions (Fig. 4). Follow-up CT scan a week later demonstrates complete resolution of posterior-flame shaped hypodensities with normal looking basal cistern that were effaced earlier (Fig. 5).

Discussion: Posterior reversible encephalopathy syndrome (PRES), posterior reversible leukoencephalopathy, reversible posterior cerebral edema syndrome and hypertensive encephalopathy are various terms that are used in describing clinical disorders of seizure, headache, visual changes and altered mental status [1-2].
     In pregnant patients with eclampsia, PRES is believed to occur after a subacute elevation in blood pressure. Because of disturbance of autoregulatory mechanism that is more dependent on neurologic component in these patients, more poorly innervated areas in the posterior circulation are most susceptible. This results in the leakage of fluid into the interstitial compartment and vasogenic edema [3]. Although vasogenic edema in PRES predominantly involves the posterior circulation, the involvement of the anterior circulation (as seen in the present case) is not uncommon and should not deter consideration of this diagnosis [4].
     Of interest, in the present case, are the associated findings of intracranial hypotension. We believe that it likely developed as a result of the epidural anesthesia given during the labor. The uniform and continuous enhancement of the pachymeninges evident on both MR and CT examination is typically seen in intracranial hypotension. PRES can progress into irreversible cytotoxic edema, but is usually transient and reversible if the underlying condition is adequately treated [5]. In this case, the patient was treated by magnesium sulphate and on follow up scan the lesions were resolved within a week.

References:

1. Dillon W, Rowley H. The reversible posterior cerebral edema syndrome. AJNR Am J Neuroradiol 1998;19:859-862. [Medline]
2. Hinchey J, Chaves C, Appignani B, et al. A reversible posterior leukoencephalopathy syndrome. N Engl J Med 1996;334:494-500. [Medline]
3. Schwartz RB, Feske SK, Polak JF, et al. Preeclampsia-eclampsia: clinical and neuroradiologic correlates and insights into the pathogenesis of hypertensive encephalopathy. Radiology 2000;217:317-376. [Medline]
4. Covarrubias DJ, Luetmer PH, Campeau NG. Posterior reversible encephalopathy syndrome: prognostic utility of quantitative diffusion-weighted MR images. AJNR Am J Neuroradiol 2002:23:1038-1048. [Medline]
5. Yaffe K, Ferriero D, Barkovich AJ, Rowley H. Reversible MRI abnormalities following seizures. Neurology 1995;45:104-108. [Medline]